Silicon carbide (SiC) is characterized in that a breakdown electric field is one digit greater than that of silicon (Si), and a band gap and thermal conductivity are about three times more than those of Si. Therefore, silicon carbide (SiC) is expected to be applied to, for example, power devices, high-frequency devices, and devices that operate at a high temperature. In recent years, the SiC epitaxial wafer has been used in the above-mentioned semiconductor devices.
A SiC epitaxial wafer is produced by a SiC single crystal substrate on which a SiC epitaxial film is formed, and SiC single crystal substrate is obtained by processing a SiC bulk single crystal manufactured by, for example, a sublimation method. In general, the SiC epitaxial wafer is produced by growing a SiC epitaxial film serving as an active region of a SiC semiconductor device on a SiC single crystal substrate, using a chemical vapor deposition (CVD) method.
A horizontal rotating and revolving epitaxial growth apparatus (see a SiC epitaxial wafer-producing apparatus illustrated in FIG. 1) which horizontally arranges a plurality of wafers and rotates each wafer on its axis while revolving the wafer is given as an example of an apparatus for producing the SiC epitaxial wafer. In general, in the epitaxial growth apparatus, a plurality of satellites which are SiC single crystal substrate-mounting portions and are made of graphite are provided on a rotatable mounting plate (susceptor) made of graphite so as to surround a rotating shaft of the mounting plate. A disk-shaped ceiling made of graphite is provided above the mounting plate and the satellites. A gas supply portion for supplying a raw material gas onto the SiC single crystal substrate is provided at the center of the ceiling. Since the satellite can be rotated on its axis by a rotating mechanism, the SiC single crystal substrate placed on the satellite is configured such that it can revolve on its axis and around the rotating shaft of the mounting plate. Therefore, the SiC single crystal substrate placed on the satellite can revolve around the rotating shaft of the mounting plate and rotate on its axis.
In the above-mentioned epitaxial growth apparatus, the raw material gas is supplied from the gas supply portion so as to pass through the upper surface of the SiC single crystal substrate placed on the mounting plate from the outer circumferential end of the SiC single crystal substrate. At that time, an epitaxial material is deposited on the substrate while the SiC single crystal substrate is maintained at a high temperature by heating means. In this way, an epitaxial film is formed.
However, in this apparatus, in general, each member, such as the mounting plate (susceptor) or the satellite made of graphite, is exposed to a high temperature. Therefore, each member is coated with a film, such as a TaC film, in order to prevent deposition caused by graphite in the epitaxial film. For example, PTL 1 and PTL 2 disclose a technique which coats the surface of a member of an epitaxial growth furnace made of graphite with SiC or TaC. PTL 3 and PTL 4 disclose a technique in which a satellite is preferably used as a portion of a susceptor and the surface of the satellite is coated with, for example, SiC or TaC. PTL 5 to PTL 7 disclose a technique which coats a portion of a member made of graphite in order to protect the member.